1. Field of the Invention
The invention relates to the beneficiation of ores. More particularly it relates to the beneficiation of phosphate ores, and still more particularly to an improved benefication process which comprises use of an etherdiamine, as a selective collector in a single flotation step, in combination with an aqueous alkali metal silicate wash of the feed prior to flotation.
2. Discussion of the Prior Art
Phosphate ore is found in various places in nature, and it contains a valuable raw material for producing many products, principally fertilizer. The most useful constituent of the ore is calcium fluorophosphate; those of no value include calcium carbonate, carbonaceous materials, heavy minerals, siliceous materials such as silica, and clay. Removal of these valueless materials is necessary and has been the subject of extended research.
As everyone in the phosphate mining and recovery arts knows, before about 1930 recovery of such phosphate was little better than 20%. About this time, the flotation system was developed by the predecessor to International Minerals Corporation. Flotation separated phosphate rock from clays and the like by treating them with chemicals to cause them to float. This was done by frothing, or creating air bubbles, to which the phosphate could cling for floating.
As taught in U.S. Pat. No. 3,817,972, partial concentration is first employed to remove phosphate and this is followed by two separate beneficiation steps. The first one is the fatty acid flotation of phosphate values using an acid and a strong base (caustic soda or ammonia) in combination with a petroleum fraction such as fuel oil. The fraction obtained, or rougher concentrate, still contains considerable siliceous material and, after deoiling this rougher concentrate, is treated in a second flotation using long chain fatty acid amines or salts thereof. This has been used since about 1942 and still is the standard procedure in use in the phosphate recovery industry. No art is known that teaches or suggests using an etherdiamine in a single flotation step.
U.S. Pat. No. 4,227,996 teaches a method of beneficiation in which an ether tri- or tetramline is used in a beneficiating process having at least two floats.
One-step flotation or one-agent methods using amines are known. For example, U.S. Pat. No. 2,313,260 discloses a method for preferentially floating the siliceous material away from phosphate ores using octadecylamines. However, the pH had to be maintained at a high level (8.5-11), and the ground one was preferably conditioned with alkaline solution, washed with water and slurried prior to flotation. Also, U.S. Pat. No. 4,227,996 is directed toward flotation with a single agent, i.e., a polyamine adduct of a long chain monoepoxide and a polyalkylene polyamine, and this product may then be reacted with water. One product disclosed has the formula: ##STR1## The disadvantage of the patented process, however, is that at least two floats using the amine reagent are required for optimum recovery of phosphate values.